Machine for cutting screw threads



' L. B. CURTIS MACHINE FOR CUTTING SCREW THREADS Filed Dec. 8, 1924 2 Sheets-Sheet 1 INVENTOR. 133.6 3

Jan. 12 ,1926.

L. B. CURTIS MACHINE FOR cum me SCREW THREADS Filed Dec. 3, 1924 2 Sheets-Sheet 2 K M M mfi M Vr M Ma T C A B L Patented Jan. 12, 1926.

PATENT OFFICE.

, LEWIS B, CURTIS, 0F BRIDGEPORT, CONNIEIGTICUT.v

MACHINE EOR CUTTING SCREYV THREADS Application filed December To all whom it may concern:

Be it known that I, LEWIS B. CURTIs, a citizen of the United States, residing in the city of Bridgeport, county of Fairfield, and State of Connecticut, have invented certain new and useful Improvements in Machines for Cutting Screw Threads; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to pipe threading machines, and has for one of its objects the provision of means whereby the chasers may be automatically disengaged or released from the pipe at the end of the threading operation. A further object of the invention is to provide, in connection with such releasing mechanism, a device which may be adjusted or set so as to actuate said mechanism, at any desired point of the threading operation and thus control the length of thread to be cut, at the option of the operator. V

lVhile my improved die release may be adapted to pipe threading machines of various types, I have illustrated the same in connection with a machine in which the dies or chasers are mounted in a revoluble head, while the pipe to be threaded is held stationary (in the vise jaws J of the machine) against rotation as well as against longitudinal movement.

In the drawings,

Figure 1 represents a front view of a machine of the type mentioned embodying my invention Figure 2 is a side view of the same- Figure 3 is an enlarged View of the main gear carrying the dies and the releasing mechanism, and

Figure 4 is a section on line 4-4 of Figure 3.

Referring to the drawings, 10 denotes the die carrier mounted for rotation andlongitudinal movement within a shell 11 having feet 11 for securing the same to a bench or stand. This carrier is in reality a gear the teeth of which are in engagement with a pinion 12 journaled in suitable bearings 13 of the shell and operated by power, 1t being understood that the die-carrier is rotated in the shell clockwise to cause the dies or chasers D to cut a right hand thread on the 8, 1924. Serial No. 754,583. v

pipe P, or anti-clockwise to cut a left hand thread, the dies being right hand or left hand, as the case may be.

The dies D are mounted for sliding movement in radial slots of the carrier 10 and may be thusmoved by a cam ring 14 rotatable on the carrier and having aseries of cam faces 14 for holding the several dies D against outward movement, respectively, the organization being such that, when the cam ring is rotated on the gear, clockwise, (as per arrow a) all the dies will be'contractcd or moved inwardly toward the center of the gear, .1 simultaneously. Reversely, when the cam is moved anti-clockwise, (as per arrow 6) all the dies will be pulled outwardly or opened, by camgrooves 14 in engagement with pins 15 carried by the several dies, respectively, (see Figures 3 and 4). A face-plate 16 secured to the front face of the main gear by screws 16, serves to retain the dies and the cam for free sliding movements on the main gear. It will'now be understood that, when the cam is moved anti-clockwise relatively to the gear, the dies will be opened.

The mechanism for accomplishing this result comprises, in its preferred form, a lever having a hub 20 which is journaled on a stud 21 indirectly secured to the main gear through the intervention of a bridge 22 which is rigidly screwed to the main gear, as shown. The lever hub 20 just mentioned has an arm 20 and a link 23 has its ends pivoted respectively to said arm and to a plate 24 which may be adjusted arcuately in the slot 25 of a segment 25 secured to the cam ring 14, a pair of binding nuts 26 serv ing to hold the plate 24 in its adjusted position.

Normally, when the cam is in position to hold the dies in their standard pipe-size positions for threading, the stud 21 and the end pivots of the link 23 will be disposed in a straight central line, as shown, and they may be thus held frictionally by a spring pressed plunger, or ball 27 (see Figure 4) adaptedto be seated in a shallow recess 28 provided at that particular position in the front face of the bridge 22, to hold the organization against'accidental displacement the ball being forced into said recess by a spring 29 the tension of which may be varied by filler disks 30.

When, now, the lever arm 21 is swung in either direction relative to that central line, the cam ring will be positively pulled anti-clockwise and therefore open all the dies, simultaneously. While such swinging movement may be imparted to the lever arm 20 by the operator, yet I have provided a tripping device whereby it may be performed not only automatically, but which may be adjusted to provide for cutting dif ferent lengths of thread, it being understood, of course, that for the same position of the tripping device, the successively cut threads will all be of the same length.

In its preferred form the tripping device consists of pin seated in a recess provided in the front of the shell and adapted to be adjusted therein, as far as its outward projection is concerned. A set screw 36'holds the pin 85 in its adjusted position. This pin is adapted to engage and throw an arm 20 of the lever hub 20 above mentioned into the position shown by the dotted lines in Figure 3, when the main gear is rotating clockwise to have its dies to cut a right hand thread, but only after the gear has entered into the shell sufliciently to cut a thread of proper length. In other words, when the threading operation begins, the front face of the main gear is flush with the front face of the shell. The trip pin is then adjusted so that the distance L from the front face of the pin to the rear face of the arm 20 is equal to the desired length of the thread to be cut, and the set screw is then applied. The main gear is then rotated by power, and gradually forced rearwardly in the shell by hand pressure applied to a bow lever 40 pivoted at its opposite ends on studs 41, and connected (by links 42) with a pair of sliding bars 43 which carry shoes 44 fitting a peripheral groove 44 in the main gear, or more particularly in a wear ring 45 rigidly carried by the main gear and effectively sealing the tooth spaces of said gear against chips or other extraneous matter. A similar ring L6 is provided at the rear end of the gear, except that this ring does not require the shoe groove above mentioned.

The hand pressure on the bow lever 40 needs'to be maintained only long enough to let the dies out three or four threads on the pipe end, as after that the main gear will be moved along in the shell by the dies fol lowing the already cut threads, in exactly the same manner as an ordinary die stock feeds itself on after the thread has been once started. This feeding on movement will continue until the end of the arm 20 (as it stands radially from the rotation axis of the main gear) ultimately encounters the front end of the trip pin 35 and is thereby then swung around its pivot, and leaves the mechanism in the position shown by dash lines C, the dies being then free from the pipe and the right hand threading operation stopped.

1f the movement of the main gear should be anti-clockwise (as per arrow 6) for cutting a left hand thread, the arm 20 will, by the trip pin 35, be swung in the opposite direction to bring the seve al parts into the position shown by dot-and-dash lines cl the result of shifting the cam relatively to the main gear being the same as before.

By virtue of the slotted sector 25, the cam may be adjusted to bring the dies into the desired standard positions, without affecting the straight line lock organization of the arm 20 and the pivots of the link 23, it being understood that, during such adjusting movement, the binding nuts 26 are loose.

Changes may be made in the construction of the several elements, as well as in their general organization, without departing from the spirit of the invention as defined by the appended claims.

Having thus described my invention what I claim as new is 1. A machine of the character described, comprising a stationary shell, a rotary die carrier circumferentially journaled within said shell and capable of lengthwise movement therein, threading dies positioned within said carrier, a cam supported by said carrier and capable of independent rotary movements for radially moving said dies simultaneously, a lever pivoted on the die carrier and connected with said cam, a rotary hub jo urnaled to the outer face of said carrier near the periphery thereof, connections between said hub and lever whereby the rotary movements of the hub will effect the operation of said lever to open the dies, an adjustable pin located within said shell and projecting from the outer face thereof, and a member extending from said hub and adapted to strike said pin at a predetermined time during the inward movement of said carrier, whereby said hub will be independently rotated.

2. A machine of the character described, comprising a stationary shell, a stationary vise for holding the work, a rotatable die carrier circumferentially journaled within said shell and having a movement therein toward and away from said vise, diescarried by the die carrier, a cam supported by said carrier for radially moving said dies simul taneously, a rotary member extending from the outer face of said carrier near the periphery thereof, connections between said member and cam whereby the rotation of said member will effect the operation of the cam, and a device adj ustably held in the shell and cooperating with said member to rotate the latter at a predetermined time during the inward movement of the die carrier.

3. A machine of the character described,

comprising a shell, a vise for holding the inward movement of the die-carrier in the work, a die-carrier movable toward and shell, and means for varying the position of 10 away from said vise and rotatable in said said trip-pin for effecting the operation of shell, dies carried by the die-carrier, a cam said cam at diflerent periods of the threadsupported by the said die-carrier for radially ing operation. moving said dies simultaneously, a trip-pin In testimony whereof I afiiX my signature supported in said shell for moving said cam hereto.

to open said dies during the rotation and I LEWIS B. CURTIS. 

